Because flourine-containing elastomer, especially perfluoro elasotmer which is composed mainly of tetrafluoroethylene (TFE) units, demonstrates excellent chemical resistance, solvent resistance and heat resistance, it is widely used as a sealing material and the like under harsh circumstances.
However, the characteristics in demand have become more severe as technology advances, and in the fields of aerospace, semiconductor manufacturing devices and chemical plant, sealing property under high temperature circumstances of at least 300° C. is desired.
In response to such demands, an approach to improve heat resistance by exercising ingenuity to the crosslinking system has been suggested. As methods of these, a toriazine crosslinking system, using a flourine-containing elastomer with a nitrile group introduced as the crosslinking point, to form a triazine ring in the presence of an organic tin compound (for example JP-A-58-152041) is known. Other known crosslinking systems are, for example, an oxazole crosslinking system in which an oxazole ring is formed in the presence of bisaminophenol, (for example JP-A-59-109546), an imidazole crosslinking system in which a imidazole ring is formed in the presence of a tetramin compound, (for example JP-A-59-109546), and an thiazole crosslinking system in which an thiazole ring is formed in the presence of bisaminothiophenol, (for example JP-A-8-104789). In these latter systems flourine-containing elastomer with a nitrile group is also introduced as the crosslinking point.
Of these crosslinking systems, when crosslinking a nitrile group containing perfluoro elasotmer with a tetramin compound, the heat resistance of the obtained molded article of the crosslinked rubber will improve in comparison to the conventional. However, in high temperatures exceeding 300° C., deterioration is intense in contrast to a toriazine crosslinking system or an oxazole crosslinking system.
An object of the present invention is to provide a crosslinkable elastomer composition to produce a molded article of the crosslinkable rubber, improved especially in mechanical strength and heat resistance at a high temperature.
Another object of the present invention is to provide a new crosslinking agent.